Electronic components are usually produced from approximately circular semiconductor disks, so-called wafers. These substrates must be fed to various processing plants, in which the substrates are essentially surface-treated. In this connection, it is often necessary to store the substrates temporarily, if, after completion of the processing in a processing plant, the substrates cannot be fed immediately thereafter to another processing plant. It is common to store the substrates temporarily in a storage device under clean or ultraclean room conditions (all in all, called “clean room conditions” below). Since the costs for producing the clean room conditions essentially depend on the size of the room, an effort is usually made to store the substrates with as little distance between one another as possible.
In spite of the fact that the distance is as little between one another as possible, it is often necessary to be able to remove specific individual wafers from the storage device, without removing other substrates in this case. Therefore, the distance between consecutive substrates within such storage devices is limited by an access distance still being present, into which a gripper can be inserted in order to detect and to remove the corresponding substrate.
In order to be able to optimize processing processes, so-called test wafers are used. No electronic components are usually manufactured from such test wafers. They are only used to empirically optimize process parameters, by processing test wafers with different process parameters, and by determining, based on measurements, which values of the process parameters will be used in the wafers that will actually be processed. Apart from the wafers mentioned, test wafers of this type are also another important field of application for the present invention.
Moreover, it may be necessary to transport wafers in a container inside or even outside of a factory. For this as well, transport containers, which have a plurality of storage elements, on each of which a substrate can usually be arranged, are used. Transport containers of this type are often standardized, for example, as so-called FOUP (front opening unified pod) transport boxes. Also here there is the need to be able to arrange the substrates with as little distance from one another as possible.